We fabricated a 120nm pin a-Si:H solar cell using PECVD, after that test the open circuit voltage. It was about 0.3 volt but our problem is about very very low short circuit ( about 0.1 uA for a 0.25 cm2 cell), Can anyone help about this?
Dear Mehrdad,
Before discussing the issue one wold like to see the dark i-v curve and the illuminated i-v curve. However one notice that the thicness of the pin diode is too small. It is so that the p+ and n+ layers can touch causing internal short of the diode. Also, pin holes and voids cause the upper metal electrode to touch the lower electrode causing also additional short of the junction. In addition the too small i-layer absorbs only smaller part of the incident solar radiation causing the reduction of he photo current.
After displaying the i-v curves one may be able to judge on the such low short circuit current.
Best wishes
Hello Mehrdad,
I think you should also consider the carrier lifetime value of the type of solar cell you are using which has relationship with the excess charge carrier density. This is because carriers take some time to travel across the silicon wafer and they reach the pn junction only if their life expectancy is long enough to complete the journey.
Thank a lot for your answers. I will execute your comments and tell about results
Would you display a typical and illuminated i-v curves and tell us what did you change according to the first trails?
thank you
At the moment we don`t have any I-V curve. We just check Jsc and Voc after fabrication with a multi-meter. When we fabricated a cell (using PECVD method), SiH4+H2 powder formed in the chamber. At first we think this powder produce pin holes in the structure so we control the plasma then the powder did not produce any more. But the Jsc is still about zero. After that we think this is because of schottky contact. We used Ag, Cu, Al, Mg as back contact but the result was disappointing.
It seems me that yor material is not amorphous hydrid - silicon. The SiH4 is a gas and can be never powder. If you have powder and your reaction chamber is air tight then the rate of reaction is very high in the gas phase leading to pyrolesis of silane forming silicon rain. You have to control your reaction rate and even reduce it further to get the intended material. If you get amorphous silicon without sufficient hydrogenation. the lifetime of the minority carriers will be very short rendering the photvooltaic effect not achievable. Yes you have to adjust car-fully your deposition condition to get firstly H:amororphous SI
Best wishes
check the thickness as have been observed, the the luminescence of the sputter plasma can cause damage so you need to give it a low temperature annealing treatment. you may also use this link may be its helpfull
pvlab.epfl.ch/heterojunction_solar_cells
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